Battery driven ground power unit with improved construction, operability, durability and maintenance

ABSTRACT

An airport ground power unit for supplying electric current to a parked aircraft and a related system and method. The ground power unit includes a first electric battery, an inverter for transforming an output current of the battery to an alternating output current to be supplied to the aircraft, and one or more first electronic switches for connecting and disconnecting the first battery to and from the inverter. The first switches are connected in serial to the first battery, and together connected to the inverter. A first controller unit controls at least one of the one or more first switches. The ground power unit further includes a second electric battery and second electronic switches for connecting and disconnecting the second battery. The second switches are connected in serial to the second battery and are together connected to the inverter such that they are in parallel to the serially connected first battery and the first switches. At least one of the second switches is controlled by the first or a second digital controller unit.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.16/649,066, filed on 19 Mar. 2019, which is a National Phase applicationof PCT/US2018/054668, filed on 5 Oct. 2018. The co-pending parentapplication is hereby incorporated by reference herein in its entiretyand is made a part hereof, including but not limited to those portionswhich specifically appear hereinafter.

BACKGROUND OF THE INVENTION Field of the Invention

This invention relates to aircraft ground power units (GPUs).

Discussion of Related Art

In the related art “Referenzbericht: eGPU Energieversorgung vonFlugzeugen” by ARADEX AG, CH, a battery driven ground power unit ispresented.

SUMMARY OF THE INVENTION

The inventors wanted to improve construction, operability, durabilityand maintenance of such battery driven GPU. The object of the inventiontherefore was to provide a GPU with improved construction, operability,durability and maintenance.

In this application the term battery GPU generally relates to a GPUcomprising one or more batteries. It may in addition be a hybrid GPU,containing in addition a combustion engine and generator.

Particularly, this object is achieved by an Airport battery GPU,preferably mobile on wheels, for supplying electric current to anaircraft parked on the ground, the GPU comprising

-   -   a first electric battery,    -   an inverter for transforming an output current of the battery to        an alternating output current of the inverter to be supplied to        the aircraft,    -   one or more first electronic switches for connecting and        disconnecting the first battery to and from the inverter,        wherein the one or more first switches is or are connected in        serial to the first battery and wherein the serially connected        first battery and the one or more first switches are together        connected to the inverter,    -   a first controller unit for controlling at least one, preferably        all, of the one or more first switches;    -   a second electric battery and    -   one or more second electronic switches for connecting and        disconnecting the second battery to and from the inverter,        wherein the one or more second switches is or are connected in        serial to the second battery and wherein the serially connected        second battery and the one or more second switches are together        connected to the inverter such that they are in parallel to the        serially connected first battery and the one or more first        switches, wherein at least one, preferably all, of the one or        more second switches is controlled by the first digital        controller unit or by a second digital controller unit, wherein        in addition to the one or more first switches being connected in        serial to the first battery, a first diode is connected in        serial, allowing current from the first battery to the inverter        and blocking or limiting current from the inverter or the second        battery to the first battery; and wherein in addition to the one        or more second switches being connected in serial to the second        battery, a second diode is connected in serial, allowing current        from the second battery to the inverter and blocking or limiting        current from the inverter or the first battery to the second        battery.

The object of the invention is also particularly achieved by a method ofoperating a GPU in order to supply current to an aircraft parked on theground, the GPU comprising the steps:

-   -   by a first digital controller unit, switching one or more first        electronic switches for connecting and disconnecting a first        battery of the GPU to and from an inverter of the GPU,    -   transforming an output current of the first battery to an        alternating output current of the inverter,    -   by the first controller unit or by a second controller unit,        switching one or more second electronic switches for connecting        and disconnecting a second battery of the GPU to and from the        inverter,    -   by a first diode of the GPU, allowing current from the first        battery to the inverter and blocking or limiting current from        the inverter or the second battery to the first battery,    -   by a second diode of the GPU, allowing current from the second        battery to the inverter and blocking or limiting current from        the inverter or the first battery to the second battery,    -   transforming an output current of the second battery to the        alternating output current of the inverter.

Hereby, construction, operability, durability and maintenance of thebattery GPU are improved. For example, if one battery is disconnected,for some reason, during load, the remaining battery (or batteries, seebelow) can remain unaffected. Fully charged batteries can be on hold asa reserve connected to the inverter during an aircraft turnaround ifneeded. The diodes thereby prevent reverse charging or reverse chargingwith unlimited current, which would be harmful to the battery and/orlead to reduced efficiency.

Preferably, in that same manner, the GPU comprises a third battery withone or more third switches and third diode and/or a fourth battery withone or more fourth switches and fourth diode and/or further batterieswith one or more further switches and further diodes connected inparallel to the first and second battery and respective switches.Features that in the following are described as preferred for the firstand second battery scenario, preferably also apply, in case of more thantwo batteries, to the third, fourth or further battery scenariosaccordingly.

The first battery and second battery are preferably each configured tosustain 90 kW at the GPU's output port, leading to the airplane.Preferably, the first battery and second battery are built in the sameway having the same electrical specifications. The first battery and/orsecond battery are preferably battery packs, each built from multiplebattery cells.

The inverter is preferably configured to output 400 Hz ac, preferably3×200 Vac (phase-to-phase) @ 400 Hz, preferably at at least 90 kVA.

The first/second diode is at least (configured for) limiting the currentfrom the inverter or from the second/first battery to the first/secondbattery, e.g. by forcing any reverse current via a first/second shuntresistor, which could be a classic quasi-linear resistor or anothercurrent limiting element or current limiting circuit of elements.Particularly preferably, the first/second diode is (configured for)completely limiting the current from the inverter or from thesecond/first battery to the first/second battery, e.g. realized in thatno reverse current permitting shunt path exists parallel to therespective diode.

Preferably, the GPU does not comprise a combustion engine drivengenerator set with a continuous electric power output higher than 50%,preferably 30%, of the output power rating of the GPU.

Preferably, one or more, of the first switches and the first diode arerealized in one element, e.g. a transistor (preferably IGBT) orthyristor. The same is preferred for the second switches and secondfirst diode.

Preferably, one or more of the first switches and the first diode arerealized by an electronic relay (electro-mechanic or solid-state) and,if not the relay is already unidirectional, a separate, seriallyconnected diode. The same is preferred for the second switches andsecond first diode. Preferably, at least one of the one or more firstswitches and at least one of the one or more second switches is realizedas an electro-mechanic relay.

The output current of the battery could be led directly or indirectly(e.g. over a filter or another intermediate element) to the inverter.

Preferably, each battery has a battery monitoring device dedicated to itand the GPU is configured to disconnect any of the batteries by way ofopening one of the first or second switches in case the batterymonitoring device indicates a malfunction of the respective battery.

In a further preferred embodiment according to the present invention thecapacity of all batteries of the ground power in total is at least 80kWh.

Hereby, the battery is able to store sufficient energy to sustain acouple of aircraft turnarounds by only battery stored energy.

In a further preferred embodiment according to the present invention atleast one of the one or more first switches and at least one of the oneor more second switches are each configured to disconnect both poles ofthe respective battery from the inverter. In a further preferred methodaccording to the invention both poles of the respective battery areconnected to and disconnected from the inverter.

Hereby, safety of the GPU is improved. A complete disconnection of thebattery from the other electrical circuits can be advantageous inemergencies.

In a further preferred embodiment according to the present invention theGPU comprises a battery charger configured to charge the first batteryand the second battery. In a further preferred method first and secondbattery are charged by the same charger, either at the same time oralternating.

Preferably, the GPU comprises a switch, preferably a 2-pole switch,

-   -   a) for connecting and disconnecting the charger to and from the        first/second battery;    -   b) or for connecting and disconnecting the charger to and from a        power source, inputting power to the charger.

Particularly preferably, in case a) this switch is one of the one ormore first/second switches.

In a further preferred embodiment according to the present invention theGPU comprises a first battery charger configured to charge the firstbattery and a second battery charger configured to charge the secondbattery. In a further preferred method according to the invention thefirst battery is charged by a first battery charger of the GPU and thesecond battery is charged by a second battery charger of the GPU.

Hereby, fast and easy charging is achieved. By the GPU comprising onecharger per battery, it is possible to charge the batteries from the50/60 Hz mains and in addition, the batteries can be charged in a fastmanner independently from each other. One charger per battery improvesutilization of the total battery capacity, i.e. when charging of abattery needs to “slow down” due to a high cell voltage, charging of theremaining packs can continue unaffected.

Preferably, the first controller is configured to control the firstcharger and the second controller is configured to control the secondcharger. Preferably, the chargers are connected to one common ordifferent connector of the GPU for connecting the charger to the gridpower.

Preferably, the GPU comprises,

-   -   a) a switch, preferably 2-pole, for connecting and disconnecting        the first charger to and from the first battery and a switch,        preferably 2-pole, for connecting and disconnecting the second        charger to and from the second battery,    -   b) or one or more switches for, together or separately,        connecting and disconnecting the first and second charger to and        from a power source, inputting power to the charger first and        second charger.

Particularly preferably, in case a) the switches are ones of the one ormore first/second switches.

Hence, preferably, at least one of the one or more first switches isconfigured to disconnect the, preferably first, charger from the firstbattery, and at least one of the one or more second switches isconfigured to disconnect the, preferably second, charger from the secondbattery.

In a further preferred embodiment according to the present invention theGPU comprises a combustion engine driven generator set or a fuel cellwith a continuous electric power output smaller or equal than 50%,preferably 30%, of the output power rating of the GPU, wherein thegenerator set is configured to feed the charger or the first and/orsecond charger and/or configured to feed power directly into the commonDC-bus (i.e., the batteries' output and/or the inverter's input) via arectifier. In a further preferred method according to the invention thecharger or the first and/or second charger is fed by an accordinggenerator set of the GPU.

Hereby a cost efficient and compact way of charging the batteries isprovided, by a very small engine or fuel cell, which would not bepowerful enough to sustain an aircraft for which the GPU is rated for,but powerful enough to charge the batteries up to a certain chargestatus.

In a further preferred embodiment according to the present invention atleast one of the one or more first switches is configured to disconnectthe first battery from the inverter while

-   -   connecting the charger or the first battery charger to the first        battery    -   and/or not disconnecting the charger or the first battery        charger from the first battery    -   and wherein at least one of the one or more second switches is        configured to disconnect the second battery from the inverter        while    -   connecting the charger or the second battery charger to the        second battery    -   and/or not disconnecting the charger or the second battery        charger from the second battery. In further preferred method        according to the invention, switching the at least one of the        one or more first switches is disconnecting the first battery        from the inverter while connecting the charger or the first        battery charger to the first battery and/or not disconnecting        the charger or the first battery charger from the first battery        and switching the at least one of the one or more second        switches is disconnecting the battery from the inverter while        connecting the charger or the second battery charger to the        second battery and/or not disconnecting the charger or the        second battery charger from the second battery.

Hereby, it is possible to charge the batteries while they are not beingdischarged.

In a further preferred embodiment according to the present invention theone or more second switches are controlled by the second controllerunit, wherein the GPU comprises a first battery monitoring device formonitoring a correct function of the first battery, wherein the firstcontroller is connected to the first battery monitoring device via afirst communication line for communication with the first batterymonitoring device and configured to disconnect the first battery,preferably from the inverter and/or the charger, by opening at least oneof the one or more first switches, as soon as the first batterymonitoring device indicates a malfunction of the first battery, whereinthe GPU comprises a second battery monitoring device for monitoring acorrect function of the second battery, wherein the second controller isconnected to the second battery monitoring device via a secondcommunication line for communication with the second battery monitoringdevice and configured to disconnect the second battery, preferably fromthe inverter and/or the charger, by opening at least one of the one ormore second switches, as soon as the second battery monitoring deviceindicates a malfunction of the second battery. In further preferredmethod according to the invention the batteries accordingly monitoredand upon a malfunction the switches are accordingly switched todisconnect the respective battery.

Hereby, safety of the GPU is improved, as each battery has its ownsafety shut-off system.

Preferably, the first and second battery monitoring devices are batterymanagement controllers configured to monitor one or more of thefollowing:

-   -   Voltage: total voltage, voltages of individual cells, minimum        and maximum cell voltage or voltage of periodic taps,    -   Temperature: average temperature, coolant intake temperature,        coolant output temperature, or temperatures of individual cells,    -   State of charge (SOC) or depth of discharge (DOD), to indicate        the charge level of the battery,    -   State of health (SOH), a variously-defined measurement of the        overall condition of the battery,    -   Coolant flow: for air or fluid cooled batteries,    -   Current: current in or out of the battery,    -   insulation resistance: isolation between battery pole and        housing and configured to indicate to the respective first and        second controller if any of the foregoing or a value computed of        one of the foregoing is out of its allowed boundaries to        indicate a malfunction.

Preferably, the first communication line is galvanically isolated fromthe second communication line. This further improves safety.

Preferably, the first and second controller each communicate to therespective battery monitoring device via a communication bus (e.g. CANbus).

In a further preferred embodiment according to the present invention theGPU comprises a digital central controller, wherein the centralcontroller is connected to a user interface, and is configured to becontrolled by a user using user interface, and is connected to the firstcontroller and to the second controller via a communication bus. Infurther preferred method according to the invention the GPU isaccordingly used by a user and the central controller accordinglycommunicates with the first and second controller.

Hereby, safety is further improved as the overall control of the GPU byuser is going through separate central controller, relieving the firstand second controller from these tasks.

The central controller is preferably configured to send switching to thefirst and second controller for connecting or disconnecting and/orcharging the first or second battery. The first controller and secondcontroller are configured to receive these commands and switch the oneor more first and second switches and or control the first and secondchargers accordingly. Preferably, the first controller and secondcontroller are configured to reject a command for connecting ordisconnecting and/or charging the first or the second battery in case ofa malfunction of the first or second battery, indicated by the first orsecond battery monitoring device.

The central controller is preferably configured to control the inverter.

Preferably, communication lines of the communication bus between thecentral controller and the first and second controller are galvanicallyinsulated from the first and second communication lines between thefirst and second controller and the first and second battery monitoringdevice.

In a further preferred embodiment according to the present invention atleast one of the one or more first switches and the first battery form afirst battery module housed in a first housing, and wherein at least oneof the one or more second switches and the second battery form a secondbattery module housed in a second housing.

Hereby, construction, maintenance and safety are further improved. Suchmodules can be easier put into the GPU and exchanged. Further, effect ofmalfunctions, e.g. fire, can be limited by the housing. The housing ispreferably fireproof, e.g. by being metallic. Preferably, the batterymonitoring device (see above) is also part of the so formed batterymodule.

In a further preferred embodiment according to the present invention thefirst and second battery module each contain a soft-start device fortemporarily limiting the output current of the respective first andsecond battery after connecting the respective first and second batteryis being connected to the inverter by means of the one or more first andsecond switches. In a further method according to the invention, theoutput current of the respective first and second battery is accordinglylimited temporarily.

In a further preferred embodiment according to the present invention theGPU, preferably each of the first and second housing, comprises aheating device configured to be automatically switched on or suppliedwith increased power, when the temperature falls below a predeterminedtemperature (e.g., −20° C.), and to be automatically switched off orsupplied with decreased power again, when the temperature reaches atemperature above or equal to the predetermined temperature. In afurther method according to the invention, a heating element isaccordingly switched/controlled.

In a further preferred embodiment according to the present invention theGPU comprises an inductance connected serially between the inverter andthe first and second battery. In further preferred method according tothe invention, current peaks to the inverter are damped by an inductancebetween inverter and the first and second battery.

Hereby, operability of the ground power system is further improved. Adisconnected battery can be reconnected, although it has a highervoltage than the remaining packs and in that case the inductance willlimit the inrush current into the inverter to an acceptable level. Someof the battery packs can be charged while others are used to sustain theload (discharged).

In a further preferred method according to the present invention theswitching of one or more first electronic switches and the switching ofthe one or more second electronic switches comprise:

-   -   switching at least one of the one or more first electronic        switches for connecting the first battery to the inverter;    -   switching at least one of the one or more second electronic        switches for connecting the second battery to the inverter;    -   switching at least one of the one or more first electronic        switches for disconnecting the first battery from the inverter,        while continuing to transform the output current of the second        battery to the alternating output current of the inverter, and        then charging the first battery by a battery charger of the GPU;    -   after a certain time switching at least one of the one or more        first electronic switches for connecting again the first battery        to the inverter, in order to transform the output current of the        now recharged first battery to the alternating output current of        the inverter, while blocking or limiting current from the first        battery to the second battery by the second diode.

In a further preferred method according to the present invention theswitching of the one or more first electronic switches and the switchingof the one or more second electronic switches comprise:

-   -   switching at least one of the one or more first electronic        switches for connecting the first battery to the inverter;    -   switching at least one of the one or more second electronic        switches for connecting the second battery to the inverter;    -   switching at least one of the one or more first electronic        switches for disconnecting the first battery from the inverter,        while continuing to transform the output current of the second        battery to the alternating output current of the inverter, and        then charging the first battery by a battery charger of the GPU;    -   after a certain time switching at least one of the one or more        first electronic switches for connecting again the first battery        to the inverter, in order to transform the output current of the        now recharged first battery to the alternating output current of        the inverter, while blocking or limiting current from the first        battery to the first battery by the second diode.

In a further preferred method according to the present invention theswitching of the one or more first electronic switches comprise:

-   -   switching at least one of the one or more first electronic        switches for disconnecting the first battery from the inverter        and/or a charger of the GPU, upon a first battery monitoring        device for monitoring a correct function of the first battery        indicates a malfunction of the first battery; and the switching        of the one or more second electronic switches comprise    -   switching at least one of the one or more second electronic        switches for disconnecting the second battery from the inverter        and/or a charger of the GPU, upon a second battery monitoring        device for monitoring a correct function of the second battery        indicates a malfunction of the second battery.

Preferably, this control scheme is implemented in the centralcontroller.

The object of improving operability of a battery GPU is furthermoreachieved by a system for supplying electric current to an aircraftparked on the ground, comprising a battery GPU for supplying electriccurrent to an aircraft parked on the ground, preferably according to theinvention, the battery GPU comprising one or more batteries, and aninverter for transforming an output current of the one or more batteriesto an alternating output current of the inverter to be supplied to theaircraft, wherein the battery GPU comprises an alternating current inputport, wherein the battery GPU is configured to be connected to analternating current output connector of a helper GPU via the alternatingcurrent input port, in order to route an alternating output current ofthe helper GPU via the alternating current input port to the aircraft.

It is also achieved by a method of operating a system for supplyingelectric current to an aircraft parked on the ground, preferably asystem according to the invention, comprising a battery GPU forsupplying electric current to an aircraft parked on the ground,preferably according to the invention, by using one or more batteries,preferably using a method according to the invention, and the systemfurther comprising a helper GPU for supplying electric current to anaircraft parked on the ground, wherein the method comprises the steps:

-   -   connecting a helper GPU's alternating current output connector        to an alternating current input port of the battery GPU, and    -   routing an alternating output current of the helper GPU to the        aircraft via the alternating current input port.

Hereby, duration of continuous use of a battery GPU can be extended byperforming a handover of aircraft power supply from the battery orbatteries of the battery GPU to the respective power source (e.g.,battery or generator) of the helper GPU.

In a further preferred system according to the present invention, thealternating current input port comprises an aircraft socket, beingconfigured to be connected to an aircraft output connector adapted to beconnected to the aircraft.

Hereby the GPUs can be connected to each other with the existing GPUaircraft output connector. Conventional (e.g., Diesel) GPUs can beeasily used as helper GPU.

The aircraft socket is a socket of the type that is integrated in thebody of an airplane, to which the GPU's aircraft output connector isconnected for powering the aircraft. It is standardized (6 pole, 400 Hz)and known to the one skilled in the art.

The aircraft socket is preferably embedded in the housing of the GPU.Alternatively, the output cable of the GPU features the aircraft socketby way of a Y-cable configuration.

In a further preferred system according to the present invention, thebattery GPU comprises an Y-adaptor which has two alternating currentinput ports each comprising an aircraft socket, and which has anaircraft output connector, whereby an aircraft output connector of thebattery GPU is connected to one of the two alternating current inputports. Preferably the Y-adaptor comprises the input coupling switch foreach phase to be switched (e.g., 4 phases)

Hereby a battery GPU can be easily equipped with an alternating currentinput port.

In a further preferred system according to the present invention, thesystem is configured to synchronize to each other

-   -   the alternating output current of the inverter of the battery        GPU, preferably a phase angle and/or a frequency and/or a        amplitude of the output, and    -   the alternating output current of the helper GPU, preferably a        phase angle and/or a frequency and/or a amplitude of the output.

Hereby, smooth handover of power delivery between the GPUs can beprepared. It is preferred to synchronize phase angle and frequency andamplitude. However, in practice the parameter having the highest impacton a smooth transfer might be the phase angle as amplitude and frequencymight be controlled by each GPU to a sufficiently exact degree, whilethe phase angle between the currents of the two GPU is initiallyuncorrelated. Therefore, synchronizing only the phase angle of theoutput currents might already be enough for a smooth handover.

In a further preferred system according to the present invention, thesystem, preferably the battery GPU, comprises an input coupling switch,and whereby the system, preferably battery GPU, is configured:

-   -   to detect a parameter (e.g., the phase angle or frequency or        amplitude—preferably phase angle) of the alternating output        current of the helper GPU and    -   to close the input coupling switch, if the difference between        the detected parameter and a respective parameter of the        alternating output current of the inverter of the battery GPU is        smaller or equal to a predetermined threshold.

Hereby, smooth handover of power delivery between the GPUs is achieved.The step of detecting may be performed as part of the synchronization.

In a further preferred system according to the present invention, thesystem, preferably the battery GPU, is configured to shift a parameter(e.g., the phase angle or frequency or amplitude—preferably phase angle)of the alternating output current of the inverter of the battery GPUand/or, for example via a communication channel to the helper GPU'scontroller or inverter, to shift a parameter (e.g., the phase angle orfrequency or amplitude—preferably phase angle) of the alternating outputcurrent of the helper GPU.

Hereby, the synchronization of the GPUs' output currents can beaccelerated by actively shifting one or more parameters of the outputcurrents.

In a further preferred system according to the present invention, thesystem, preferably the battery GPU, comprises an output decouplingswitch, and whereby the system, preferably the battery GPU, isconfigured:

-   -   to open the output decoupling switch, if the input coupling        switch has been switched to closed state.

Hereby, the battery GPU's inverter is disconnected or deactivated suchthat correct power delivery avoiding unbalanced power draw from thebattery GPU and the helper GPU is achieved. Preferably, the outputdecoupling switch is switched within seconds or milliseconds after theinput coupling switch has been switched to closed state. Preferably, thedecoupling switch can be one of the switches of the inverter fordeactivating the inverter.

In a further preferred system according to the present invention, thesystem further comprises the helper GPU, whereby the battery GPU and thehelper GPU are connected to each other via the alternating current inputport of the battery GPU and the alternating current output connector ofthe helper GPU.

In a further preferred method according to the present inventionregarding operating a system, the connecting further comprises one ormore of the following steps a)-c):

-   -   a) synchronizing to each other, preferably by shifting a        parameter (e.g., phase angle, frequency, amplitude) of the        alternating output current of the inverter of the battery GPU        and/or, for example via a communication channel to the helper        GPU's controller, by shifting a parameter (e.g., phase angle,        frequency, amplitude) of the alternating output current of the        helper GPU:        -   the alternating output current of the inverter of the            battery GPU, preferably a phase angle and/or a frequency            and/or an amplitude of the output current, and        -   the alternating output current of the helper GPU, preferably            a phase angle and/or a frequency and/or an amplitude of the            output current;    -   b) detecting a parameter (e.g., phase angle, frequency,        amplitude) of the alternating output current of the helper GPU        and closing an input coupling switch, if the difference between        the detected parameter and a respective parameter of the        alternating output current of the inverter of the battery GPU is        smaller or equal to a predetermined threshold; and preferably    -   c) opening an output decoupling switch, if the input coupling        switch has been switched to closed state.

Preferably, the battery GPU is configured to perform phaseangle/frequency/amplitude detection, synchronization, shifting andswitching of the respective switches; and the respective hardware ispreferably implemented in the battery GPU. In that way, the helper GPUcan be a conventional GPU without additional intelligence for thispurpose. However, the scope of the invention also covers solutions wheresuch tasks are (all or only partially) performed by the helper GPU orshared between helper GPU and battery GPU. Helper GPU and battery GPUmay therefor communicate via communication channels in order to allowfor the desired operation.

The object of improving operability of a battery GPU is furthermoreachieved by an Y-adaptor which has two alternating current input portseach comprising an aircraft socket, and which has an aircraft outputconnector.

Hereby a battery GPU can be easily equipped with an alternating currentinput port.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

Embodiments of the present invention will now be described, by way ofexample only, with reference to the accompanying drawings, whereby:

FIG. 1 is a conceptual overview of one embodiment of a GPU according tothe invention;

FIG. 2 is a schematic of the electrical circuit of a preferredembodiment of a GPU according to the invention, based on the embodimentshown in FIG. 2 ;

FIG. 3 shows an embodiment of a system for supplying electric current toan aircraft parked on the ground according to the invention;

FIG. 4 shows an embodiment of a system for supplying electric current toan aircraft parked on the ground according to the invention;

FIG. 5 shows an embodiment of a system for supplying electric current toan aircraft parked on the ground according to the invention;

FIGS. 6A and 6B show an embodiment of a system for supplying electriccurrent to an aircraft parked on the ground according to the invention;and

FIG. 7 shows an embodiment of a system for supplying electric current toan aircraft parked on the ground according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a conceptual overview of one embodiment of a battery GPUaccording to the invention. It is an airport GPU 1, here mobile onwheels, for supplying electric current to an aircraft parked on theground. The GPU 1 comprises:

-   -   a first electric battery 30,    -   an inverter 50 for transforming an output of the battery 30 to        an alternating output current of the inverter 50 to be supplied        to the aircraft,    -   one first electronic switch 60 for connecting and disconnecting        the first battery 30 to and from the inverter 50, wherein the        first switch 60 is connected in serial to the first battery 30        and wherein the serially connected first battery 30 and the        first switch 60 are together connected to the inverter 50,    -   a first controller unit 10 for controlling the first switch 60.

The GPU 1 further comprises:

-   -   a second electric battery 31 and    -   a second electronic switch 61 for connecting and disconnecting        the second battery 31 to and from the inverter 50, wherein the        second switch 61 is connected in serial to the second battery 31        and wherein the serially connected second battery 31 and the one        second switch 61 are together connected to the inverter 50 such        that they are in parallel to the serially connected first        battery 30 and the first switch 60, wherein the second switch 61        is controlled by the first digital controller unit, wherein    -   in addition to the first switch 60 being connected in serial to        the first battery 30, a first diode 70 is connected in serial,        allowing current from the first battery 30 to the inverter 50        and blocking (in case without the optional first shunt resistor        70.1) or limiting current from the inverter 50 or the second        battery 31 to the first battery 30;    -   and wherein in addition to the second switch 61 being connected        in serial to the second battery 31, a second diode 71 is        connected in serial, allowing current from the second battery 31        to the inverter 50 and blocking (in case without the optional        second shunt resistor 71.1) or limiting current from the        inverter 50 or the first battery 30 to the second battery 31.

FIG. 2 shows a schematic of the electrical circuit of a preferredembodiment of a GPU according to the invention, based on the embodimentshown in FIG. 2 . In contrast to FIG. 2 , there is a second digitalcontroller unit 11 controlling the second switch 61. Furthermore, anadditional first switch 80 and an additional second switch 81 areconnected in serial between the respective battery 30, 31 and theinverter. The first controller 10 controls in addition switch 80 and thesecond controller 11 controls in addition switch 81. Further, in thatsame manner, the GPU 1 comprises a third battery with one or more thirdswitches and third diode and a fourth battery with one or more fourthswitches and fourth diode connected in parallel to the first and secondbattery and respective switches. Features that in the following aredescribed as preferred for the first and second battery scenario, alsoapply (as apparent from the Figure) to the third and fourth batteryscenario/portion.

The diodes are (configured for) completely limiting the current from theinverter or from any other battery than the one to which the diodeconnected to in serial.

The first switch and the second switch are each configured to disconnectboth poles of the respective battery from the inverter.

The GPU comprises a first battery charger configured to charge the firstbattery and a second battery charger configured to charge the secondbattery. The first controller 10 is configured to control the firstcharger 90 and the second controller 11 is configured to control thesecond charger 91. The chargers 90, 91 are connected to one commonconnector 180 of the GPU 1 for connecting the charger to the grid power.

The additional first switch 80 is configured to disconnect the firstbattery 30 from the inverter 50 while not disconnecting the firstbattery charger 90 from the first battery 30 and the additional secondswitch 81 is configured to disconnect the second battery 31 from theinverter 50 while not disconnecting the second battery charger 91 fromthe second battery 31.

The GPU 1 comprises a first battery monitoring device 170 for monitoringa correct function of the first battery 30, wherein the first controller10 is connected to the first battery monitoring device 170 via a firstcommunication line 140 for communication with the first batterymonitoring device 170 and configured to disconnect the first battery 300from the inverter and the charger by opening the first switch, as soonas the first battery monitoring device 170 indicates a malfunction ofthe first battery 30. The GPU 1 comprises a second battery monitoringdevice 171 for monitoring a correct function of the second battery 31,wherein the second controller 11 is connected to the second batterymonitoring device 171 via a second communication line 141 forcommunication with the second battery monitoring device 171 andconfigured to disconnect the second battery 31 from the inverter and thecharger by opening the second switch 61, as soon as the second batterymonitoring device 171 indicates a malfunction of the second battery 31.

The first and second controller 10, 11 each communicate to therespective battery monitoring device via a CAN bus. The firstcommunication line 140 is galvanically isolated from the secondconnection 141 line.

The GPU 1 comprises a digital central controller 110, wherein thecentral controller 110 is connected to a user interface 120, and isconfigured to be controlled by a user using user interface 120, and isconnected to the first controller 10 and to the second controller 11 viaa communication bus 130.

The central controller 110 is configured to send switching to the firstand second controller 10, 11 for connecting or disconnecting and/orcharging the first or second battery 30, 31. The first controller andsecond controller 10, 11 are configured to receive these commands andswitch the one or more first and second switches 60, 61, 80, 81 and orcontrol the first and second chargers 90, 91 accordingly. The centralcontroller 110 is configured to control the inverter 50. Communicationlines of the communication bus 130 between the central controller 110and the first and second controller 10, 11 are galvanically insulatedfrom the first and second communication lines 140, 141 between the firstand second controller 10, 11 and the first and second battery monitoringdevice 170, 171.

The first switch 60 and the first battery 30 form a first battery module160 housed in a first housing, and the second switch 61 and the secondbattery 31 form a second battery module 161 housed in a second housing.The battery monitoring devices 170, 171 are also part of the respectiveso formed battery module 160, 161.

The GPU 1 comprises an inductance 100 connected serially between theinverter 50 and the first and second battery 30, 31.

FIG. 3 shows a system for supplying electric current to an aircraftparked on the ground, comprising a battery GPU 1 for supplying electriccurrent to an aircraft parked on the ground, preferably according to oneof the preceding embodiments, the battery GPU 1 comprising one or morebatteries 30, 31, and an inverter 50 for transforming an output currentof the one or more batteries 30, 31 to an alternating output current ofthe inverter 50 to be supplied to the aircraft, wherein the battery GPU1 comprises an alternating current input port 190, wherein the batteryGPU 1 is configured to be connected to an alternating current outputconnector 191′ of a helper GPU 1′ via the alternating current input port190, in order to route an alternating output current of the helper GPU1′ via the alternating current input port 190 to the aircraft. Thealternating current input port 190 comprises an aircraft socket, beingconfigured to be connected to an aircraft output connector 191, 191′adapted to be connected to the aircraft.

The system is configured to synchronize to each other:

-   -   the alternating output current of the inverter 50 of the battery        GPU 1 and    -   the alternating output current of the helper GPU 1′.

Here, the battery GPU 1 is configured to synchronize itself to thehelper GPU 1′ and to perform a handover of power supply from the one ormore batteries 30, 31 to power delivered by helper GPU 1′.

The battery GPU 1 is configured to shift the phase angle of thealternating output current of the inverter 50. The battery GPU 1,comprises an input coupling switch 200, and the battery GPU 1 isconfigured:

-   -   to detect a phase angle of the alternating output current of the        helper GPU 1′ and    -   to close the input coupling switch 200, if the difference        between the detected phase angle and a phase angle of the        alternating output current of the inverter 50 of the battery GPU        1 is smaller or equal to a predetermined threshold. The battery        GPU 1, comprises an output decoupling switch 201 and the battery        GPU 1 is configured:    -   to open the output decoupling switch 201 if the input coupling        switch 200 has been switched to closed state.

The system is operated as follows:

-   -   Connecting the helper GPU's 1′ alternating current output        connector 191′ to the alternating current input port 190 of the        battery GPU 1, and routing an alternating output current of the        helper GPU 1′ to the aircraft via the alternating current input        port 190, while the connecting comprises    -   a) synchronizing, by shifting the phase angle of the alternating        output current of the inverter 50 of the battery GPU 1, to each        other:        -   the alternating output current of the inverter 50 of the            battery GPU 1, here a phase angle of the output current, and        -   the alternating output current of the helper GPU 1′, here a            phase angle of the output current;    -   b) detecting a phase angle of the alternating output current of        the helper GPU 1′ and closing the input coupling switch 200, if        the difference between the detected phase angle and a phase        angle of the alternating output current of the inverter 50 of        the battery GPU 1 is smaller or equal to a predetermined        threshold;    -   c) opening the output decoupling switch 201, if the input        coupling switch 200 has been switched to closed state.

FIG. 4 shows a system like the one shown in FIG. 3 whereas the inputcoupling switch 200′ is implemented in the helper GPU 1′. Furthermore,as an example, helper GPU 1′ is also a battery GPU, preferably a batteryGPU with two or more batteries 30′, 31′ according to FIG. 1 . and/orFIG. 2 . In this exemplary hardware setup, one possible operation is thesynchronization (by shifting the helper GPU's 1′ inverter 50′ phaseangle) and switching of input coupling switch 200′ by the helper GPU 1′.Via a communication channel to the battery GPU 1, helper GPU 1′ is thenswitching the decoupling switch 201 to open state. Another possibleoperation is the synchronization and switching performed by the batteryGPU 1, whereby the information about the helper GPU's 1′ inverter 50′phase angle is sent via a communication channel from the helper GPU 1′to the battery GPU 1 and switch 200′ is switched by battery GPU 1 via acommunication channel. As in this setup, there will be live male pins(=pins under voltage) of the input port 190 during operation of thebattery GPU 1 when not connected to helper GPU 1′, a mechanicalprotection, e.g. a protection lid, or an additional switch will need topresent for enhancing safety and avoiding users to get into contact withlive male pins. The same is true for the embodiments according to FIGS.5 and 6A, whereby in FIG. 6A, it is the input port 390.2 of theY-adaptor 300, which may have live male pins and needs protection.

FIG. 5 shows a system like the one shown in FIG. 4 , whereby the outputcable of the battery GPU 1 features the aircraft socket on the inputport 190 by way of a Y-cable configuration.

FIG. 6A shows a system similar to the one shown in FIG. 5 , whereby thebattery GPU 1 comprises an Y-adaptor 300 which has two alternatingcurrent input ports 390.1, 390.2 each comprising an aircraft socket andwhich has a an aircraft output connector 391, whereby an aircraft outputconnector 191 of the battery GPU 1 is connected to one of the twoalternating current input ports 390.1. FIG. 6B shows the Y-adaptor 300separately.

FIG. 7 shows a system like the one shown in FIG. 3 , whereby twoidentical GPUs are used for performing a handover from one of the GPUsto the other GPU.

What is claimed is:
 1. A system for supplying electric current to anaircraft parked on the ground, comprising a battery ground power unit(1) for supplying electric current to the aircraft parked on the ground,wherein the battery ground power unit (1) comprises one or morebatteries (30, 31), and an inverter (50) for transforming an outputcurrent of the one or more batteries (30, 31) to an alternating outputcurrent of the inverter (50) to be supplied to the aircraft, the systemcomprising an alternating current input port (190, 390.2) in combinationwith the battery ground power unit (1), wherein the battery ground powerunit (1) is configured to be connected to an alternating current outputconnector (191′) of a helper ground power unit (1′) via the alternatingcurrent input port (190, 390.2), in order to route an alternating outputcurrent of the helper ground power unit (1′) via the alternating currentinput port (190, 390.2) to the aircraft.
 2. The system according toclaim 2, wherein the alternating current input port (190, 390.2)comprises an aircraft socket, being configured to be connected to anaircraft output connector (191, 191′) adapted to be connected to theaircraft.
 3. The system according to claim 1, whereby the battery groundpower unit (1) comprises an Y-adaptor (300) which includes twoalternating current input ports (390.1, 390.2) each comprising anaircraft socket and which has an aircraft output connector (391),whereby an aircraft output connector (191) of the battery ground powerunit (1) is connected to one of the two alternating current input ports(390.1).
 4. The system according to claim 1, wherein the system isconfigured to synchronize to each other: the alternating output currentof the inverter (50) of the battery ground power unit (1), and thealternating output current of the helper ground power unit (1′).
 5. Thesystem according to claim 4, whereby the system comprises an inputcoupling switch (200, 200′), and whereby the system is configured todetect a parameter of the alternating output current of the helperground power unit (1′) and to close the input coupling switch (200,200′), if the difference between the detected parameter and a respectiveparameter of the alternating output current of the inverter (50) of thebattery ground power unit (1) is smaller or equal to a predeterminedthreshold.
 6. The system according to claim 4, wherein the system isconfigured to shift a parameter of the alternating output current of theinverter (50) of the battery ground power unit (1) and/or to shift aparameter of the alternating output current of the helper ground powerunit (1′).
 7. The system according to claim 6, whereby the systemcomprises an output decoupling switch (201), and whereby the system isconfigured to open the output decoupling switch (201), if the inputcoupling switch (200, 200′) has been switched to closed state.
 8. Thesystem according to claim 1, whereby the system further comprises thehelper ground power unit (1′), whereby the battery ground power unit (1)and the helper ground power unit (1′) are connected to each other viathe alternating current input port (190) of the battery ground powerunit (1) and the alternating current output connector (191′) of thehelper ground power unit (1′).
 9. A method of operating a system forsupplying electric current to an aircraft parked on the ground,according to claim 1, the method comprising: providing the helper groundpower unit (1′) for supplying electric current to an aircraft parked onthe ground; and connecting a helper ground power unit's (1′) alternatingcurrent output connector (191′) to the alternating current input port(190, 390.2), and routing an alternating output current of the helperground power unit (1′) to the aircraft via the alternating current inputport (190, 390.2).
 10. The method according to claim 9, further wherebythe connecting comprises one or more of the following steps a)-c): a)synchronizing the alternating output current of the inverter (50) of thebattery ground power unit (1), and the alternating output current of thehelper ground power unit (1′); b) detecting a parameter of thealternating output current of the helper ground power unit (1′) andclosing an input coupling switch (200, 200′), if the difference betweenthe detected parameter and a respective parameter of the alternatingoutput current of the inverter (50) of the battery ground power unit (1)is smaller or equal to a predetermined threshold; and c) opening anoutput decoupling switch (201), if the input coupling switch (200, 200′)has been switched to closed state.
 11. A system for supplying electriccurrent to an aircraft parked on the ground, comprising: a first batteryground power unit for supplying electric current to the aircraft parkedon the ground; a second battery ground power unit for supplying electriccurrent to the aircraft parked on the ground, each of the first andsecond battery ground power units comprising: one or more batteries; aninverter for transforming an output current of the one or more batteriesto an alternating output current of the inverter to be supplied to theaircraft; and an alternating current output port configured to deliverthe alternating output current to the aircraft; an alternating currentinput port, wherein the alternating current input port is configured toconnect to the alternating current output port of the second batteryground power unit to route an alternating output current of the secondbattery ground power unit to the aircraft via the alternating currentinput port.
 12. The system according to claim 11, wherein thealternating current input port comprises an aircraft socket, beingconfigured to be connected to an aircraft output connector adapted to beconnected to the aircraft.
 13. The system according to claim 11, furthercomprising an Y-adaptor including the alternating current input port.14. The system according to claim 13, wherein the Y-adaptor furtherincludes a second alternating current input port configured to connectto the alternating current output port of the first battery ground powerunit.
 15. A system for supplying electric current to an aircraft parkedon the ground, comprising a Y-adaptor (300) which has two alternatingcurrent input ports (390.1, 390.2) each comprising an aircraft socket,and which has an aircraft output connector (391), wherein each of thetwo alternating current input ports (390.1, 390.2) is configured toconnect to a battery ground power unit (1) comprising one or morebatteries (30, 31), and an inverter (50) for transforming an outputcurrent of the one or more batteries (30, 31) to an alternating outputcurrent of the inverter (50) to be supplied to the aircraft.